Retaining wall building block



FIG. 1 is a top plan view of a retaining wall building block showing my new design;

FIG. 2 is a bottom plan thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a left side elevational view thereof. 

The ornamental design for retaining wall building block, as shown and described. 